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Some shell commands used frequently
Raw
commands.md

Redo last command but as root

sudo !!

Open an editor(for composing) to run a long command

ctrl + x + e

Don't add command to bash history

Add a space before command

 ls -l

Fix a very long command you messed up

Fix command

fc

This will open last command in a file, you can edit that and exit. I will run the edited command

Quickly create multiple directories

mkdir -p folder/{sub1,sub2}/{sub1,sub2,sub3}

# Above command will create 6 directories

# folder/sub1/sub1
# folder/sub1/sub2
# folder/sub1/sub3
# folder/sub2/sub1
# folder/sub2/sub2
# folder/sub2/sub3

# This also works with numbers also like

mkdir -p folder/{1..100}/{1..100}

# This will create 100*100 = 10,000 new directories, 1 to 100 directories and each directory it will have 1 to 100 sub directories

Intercept stdout and log to a file

cat file.txt | tee -a log.txt | cat > /dev/null

# -a in command means append to log.txt

Exit terminal but all process running

disown -a && exit  # Disown all process then exit

Extract RPM package

rpm2cpio <package-name>.rpm | cpio -idmv
rpm2cpio php-5.1.4-1.esp1.x86_64.rpm | cpio -idmv

List contents of installed RPM

rpm -ql <package-name>
rpm -ql HSS

List contents of a RPM

rpm -qlpv <package-name>.rpm
rpm -qlpv HSS-2.5.6.0.0-1.x86_64.elf6.rpm

Check ports allocated to a process

semanage port -l | grep <process-name>
semanage port -l | grep http

Compile with gprof

Use gcc flags "-p -pg" for compiling and linking

Get top output on console

top -b -n 1 -p <pid>

List contents of tar

tar -tf <tar_name>

Run program with valgrind

valgrind --tool=memcheck --leak-check=yes --show-reachable=yes -v <program-to-run> <program-args>
valgrind --tool=memcheck --leak-check=yes --show-reachable=yes -v ./hssStub -m Load

Callgrind

valgrind --tool=callgrind <program-to-run> <program-args>
callgrind_annotate --auto=yes callgrind.out.pid

# Other options
#   --tree=both (prints, for each functions, their callers and the called functions)
#   --threshold=100 (will print all the events)

export CVSROOT

export CVSROOT=:pserver:[email protected]:/home/lte_epc

Share public key to destination machine to scp/ssh without password

  1. Generate public key
ssh-keygen
  1. Copy generated public key to destinations authorized key
cat /var/lib/jenkins/.ssh/id_rsa.pub | ssh [email protected] 'cat >> .ssh/authorized_keys'

Delete all files/directories except one or more

rm -rf !(do_not_delete_this_file_or_directory)
rm -rf !(file1.txt|file2.txt)

For above command to work, we need to enable extended pattern matching in shell using below command

shopt -s extglob

Command to see all logged in users on machine and what they are doing

w

cut command

Use -c option to print selected characters from each line

cut -c1  # Prints only first character of each line
cut -c 2,7  # Select 2nd and 7th characters
cut -c 2-7  # Select from 2nd to 7th character, both included
cut -c 2-  # Select from 2nd char to end
cut -d$'\t'  -f 1-3  # Cut with tab and select first 3 words(tab splitted)

Get weather info

curl wttr.in/delhi?lang=en

Save git username and password for future

git config credential.helper store

Use -A, -B and -C in grep to print lines after, before and between searched string

grep -A 1 "some_text" <path>  # Print 1 line after each search pattern
grep -B 1 "some_text" <path>  # Print 1 line before each search pattern
grep -C 1 "some_text" <path>  # Print 1 above and below search pattern

Use -c in grep to count occurrences

grep -c "some_text" <path>  # Prints counts of search string in each file

Use -e in grep to give multiple patterns

grep -e "text_1" -e "text_2"  # Print all lines having text_1 or text_2

Search for consecutive same digit from 0-9 like 112... or 1 1 2...

grep -E '([0-9]) *\1' *
# -E to specify a regular expression
# * with \1 to search for 0 or 1 space
# \1 to search for same digit
# Last * for path

Open files with specific string in vim (or other editor)

grep -rl myString . | xargs -o vim

vim `grep -rl myString .`

HEAD/TAIL example

head -c10  # Print first 10 characters
tail -c10  # Print last 10 characters

Tab(\t) character in cut, sort commands is specified using $

sort -t $'\t' -k 2  # With with respect to second tab separated values

Compress to .zip:

zip -r roster.zip roster.sql

Decompress .zip file:

unzip roster.zip

SED - Stream editor

sed 's/old-string/new-string/g'  # Globally replace all old with new string
sed 's/old/new/ig'  # i, Ignore case
sed 's/old/new/2'  # Replace only second instance
sed 's/str/{&}/g'  # Enclose all occurrences of str in {}

AWK - Text formatter

awk '{print}'  # Print everything
awk '{print $1 $2}'  # Print only values from column 1 and 2
awk '/xyz/ {print}'  # Print lines having string xyz
awk '{if($4 == "") print}'  # Print columns whose 4th column is empty
awk '{if($2 >= 10 && $3 >= 10) print $0; else print $4}'  # If-else

BC - Calculator

echo "10 + 20" | bc  # Calculates to 30
bc filename.txt  # filename has mathematical expressions
bc  # Opens bc console

PASTE - Pastes multiple lines

paste file1.txt file2.txt  # Pastes each word from file1 and 2 column wise
paste -s file1.txt file2.txt  # Paste all lines from 1 file at a time
paste -d "|" file1.txt  # Use | as delimeter instead of tab(default).
paste file1.txt - -  # Paste 2 consecutive lines

Run a binary in gdb with command line args

gdb --args <binary> <command line args>
gdb --args python -V  # Run python binary with -V argument

Create private key and certificate signing request(CSR)

Below command creates 2 files - domain.key has private key and domain.csr is certificate signing request file.

openssl req -newkey rsa:2048 -nodes -keyout domain.key -out domain.csr

Check open ssl connection and fetch all certificates including all intermediates

openssl s_client -connect <hostname>:<port-number>

Open a file in default application like pdf

gio open <path to pdf file>

AB load testing tool for HTTP(s) based applications

ab -k -c 2 -n 10 -s 60 http://example.com/

# -k, keep alive
# -c, concurrent connections
# -n, total number of requests to be sent
# -s, timeout in seconds for ab to complete analysis(by default it is 30)

Useful links

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